Effect of particle morphology on film cracking

Abstract

With the aim of reducing VOC emissions and producing more sustainable coatings and adhesives, solvent borne polymers are gradually being replaced by water-based alternatives. However, the mechanical properties of water borne systems are typically not as good as those of solvent borne products due to differences in the film formation process.The thesis aimed at shedding some light on film formation and cracking problem to be able to design soft core-hard “shell” latexes that yield VOC and crack free, mechanically strong coatings that can be cast at low temperatures. These are particles consisting of a soft core covered by patches of hard polymer. Different strategies have been used to overcome the film formation and cracking problem like . A mathematical model for cracking prediction and stress calculation during drying of aqueous dispersions of soft core-hard “shell” particles was developed. The model solved numerically the incompressible Navier-Stokes and continuity equations using COMSOL Multiphysics. The model was validated with experimental data. A good agreement between experimental results and model predictions was achieved.The results presented in this work highlight that careful design of soft core-hard “shell" polymer dispersions allows overcoming the film formation dilemma frequently found in water borne coatings